Explaining Acoustics, Sound and Noise

Explaining Acoustics, Sound and Noise

Acoustics is the science of sound. It allows us to measure, assess and predict not only the actual sound levels and how we are likely to respond to the physical impact of sound but also how we subjectively react to those sounds.

When we find certain sounds annoying that is when sound becomes noise. This can vary from person to person and between different environments. We measure these sounds as if we were hearing them.

When sounds are of a level that can cause physical damage we consider the levels, not as our reaction to them but the physical impact of the sound pressure on the ear. In this way, we can assess the potential for physical damage.

Environmental Sound Reporting

Environmental sound investigations typically centre on annoyance. It is in environments such as residential areas that unwanted sound more commonly called noise, needs to be measured and assessed. British Standards such as BS 4142:2014 and ProPG provide guideline levels which are set to allow for normal day-to-day activities such as eating, resting and sleeping and the use of our external amenity, a garden or balcony.

But an important note is that environmental noise may not just be an annoyance, it can be of a level that may produce hearing loss particularly if exposed to excessive levels over an extended time period. This will become clear by measurement at the location sensitive to noise.

Explaining Acoustics, Sound and Noise: Assessing sound of a waste transfer/recycling centre in context of surrounding industrial complex
Assessing sound of a waste transfer/recycling centre in context of surrounding industrial complex and nearby residential amenity 

Annoyance may only be the start of disturbance to life. Annoyance can have an adverse effect on health. The guidelines in BS 4142:2014 and ProPG are set to avoid such instances and a great deal of work has been done on human reaction to noise by the European Commission and the World Health Organisation which supports these assessments.

Measurement of transportation noise is typical across a 24-hour period. It will consider the impact of sounds in the daytime between 07:00 and 23:00 and at night between 23:00 and 07:00. In addition, short high peaks of sound are measured in the night, as these can be more disruptive than during the day.

Industrial and commercial noise is measured during the periods of operation of the activity. These measurements are often repeated a number of times to ensure the measurements are typical of the operation. The levels of the background, which are present when the activity has ceased, are also measured as the assessment is of how the activity noise relates to the normal environment at the point of assessment.

As well as the level and character of the sounds to be assessed, the context in which they occur is also reported. However similar sound environments may appear, no two assessment locations are the same. Whilst industrial and commercials sounds are isolated and assessed for their impact, the environment in which they occur may have a significant influence on its impact. Context can include similarity with sounds that already exist, or the time and duration it occurs. The response of the human ear is not equal at all frequencies and so analysis of the frequency content can illustrate the potential for annoyance.

Context may also include the need for housing which may compromise the desire to seek the maximum improvement in all areas of our environment.

Whilst TGSacoustics does not judge the merits of any contextual impacts you can expect that they will be observed accurately and reported faithfully. They will be discussed within a report and conclusions drawn from that data and research. This will allow for accurate assessment within the planning procedure.

Room Acoustics

Many acoustic environments are not specifically designed or controlled. It can affect our activities and us significantly. We hear sounds directly from the source and also from reflections off surrounding surfaces. The reflections can come as a delayed single clear repeat of the direct sound or a number of diffuse reflections often with a greater delay. Read more about Sound Propagation and building acoustics.

These reflections are in careful balance in the great auditoria we have for concerts, cinema and theatre. There is, however, growing awareness of the impact of good acoustics in the working environment. This is not only reducing levels of noisy processes to reduce the wear and tear on humans but also where concentration and privacy are necessary particularly in shared spaces.

Explaining Acoustics, Sound and Noise reverberation in an enclosed space
Sound reverberation in an enclosed space

Open plan offices require control of the direct sound to avoid distraction at other workstations. In controlling the level of this direct sound care has to be taken to avoid reducing the diffuse sound level to a point that it no longer masks the direct sound. Where this careful balance cannot be achieved fully by the installation of absorption and diffusers, white noise is often introduced into shared spaces to improve individual concentration and performance.

TGSacoustics will assess the needs of each environment objectively through measurement and calculation but also through careful research into the subjective requirements informed by the specific activities and also the expectations of those using the space.